Various deoxy derivatives of kanamycins A, B and C are already known as the semi-synthetic aminoglycosidic antibiotics which have been derived from kanamycins A, B and C. These known deoxy derivatives of kanamycins have usefully high antibacterial activities, but the antibacterial spectra of these known deoxykanamycin derivatives are of varying ranges. Besides, the known deoxykanamycin derivatives are possible to be inactive against such new resistant strains of bacteria which will possibly occur in future. Accordingly, it is always requested that new, antibacterial compounds having any more excellent properties than the known antibacterial compounds should be created and provided for uses in therapeutic treatment of bacterial infections. We, the present inventors, had an expectation that if we would succeed in synthetizing such a new kanamycin A derivative having the 3'-hydroxyl group replaced by a fluoro group, namely a kanamycin A derivative identifiable as 3'-fluoro-3'-deoxykanamycin A, this new compound should be active against some kanamycin-resistant strains of bacteria which are already known and also against some another resistant strains which will possibly occur in future. With such expectation, we have made our efforts to synthetize 3'-fluoro-3'-deoxykanamycin A with starting from kanamycin A, but we have not yet get a success in synthetizing such new compound with starting from kanamycin A itself. This is mainly because kanamycin A contains three adjacent, 2'-, 3'- and 4'-hydroxyl groups in the molecule thereof, leading to a large difficulty that only the 3'-hydroxyl group can hardly be replaced by a fluoro group, as far as the synthesis of 3'-fluoro-3'-deoxykanamycin A is to be achieved with using kanamycin A as the starting material. With kanamycin B, on the other hand, it was feasible to produce 3'-iodo- or 3'-bromo-derivative thereof with starting from kanamycin B when such a synthetic process of producing 3'-deoxykanamycin B is followed, wherein kanamycin B is used as the starting compound and firstly converted into a penta-N-protected-2",4",6"-tri-O-protected-kanamycin B derivative, of which the 3'-hydroxyl group is then alkylsulfonylated or arylsulfonylated; and wherein the resultant alkylsulfonylated or arylsulfonylated 3'-hydroxyl group of the N,O-protected kanamycin B is further reacted with an alkali metal iodide or bromide to give a 3'-iodo- or 3'-bromo-N,O-protected kanamycin B derivative which may subsequently be converted either into 3'-iodo- or 3'-bromo-3'-deoxykanamycin B through the removal of all the residual amino-protecting and hydroxyl-protecting groups therefrom or into 3'-deoxykanamycin B through the reduction of the 3'-halo group into a hydrogen atom and the removal of the residual amino-protecting and hydroxyl-protecting groups therefrom (see Japanese patent publication No. 876/82, Example 1; U.S. Pat. No. 3,929,762 U.K. Pat. No. 1,426,910). Through our experiments, however, it has been confirmed that any 3'-halogenated derivative of kanamycin A could not be produced even if the above-mentioned process of producing the 3'-iodo- or 3'-bromo-derivative of kanamycin B as disclosed in the specification of said Japanese patent publication No. 876/82 or the U.S. Pat. No. 3,929,762 is applied to kanamycin A. Besides, in the course of our researches in an attempt to exploit a route for the synthesis of 3'-deoxykanamycin A from kanamycin A, we have realized that kanamycin A is remarkedly different from kanamycin B in their behaviors to chemical reagents, and hence, due to the unique behaviors of the kanamycin A and particularly of the 2'-, 3'- and 4'-hydroxyl groups of kanamycin A, we had to develope such a method for synthesis of 3'-deoxykanamycin A which comprises some steps and procedures entirely different from those involved in the previously exploited process of synthetizing 3'-deoxykanamycin B from kanamycin B (see, for example, Japanese patent application first publication "Kokai" Nos. 68698/81; 118097/81 and 152497/81, U.S. Pat. No. 4,349,666; U.K. Pat. No. 2,061,942B, U.S. Pat. No. 4,357,466; U.K. Pat. No. 2,064,518B, U.S. Pat. No. 4,337,336; U.K. Pat. No. 2,070,007B, U.S. Pat. No. 4,359,572; U.K. Pat. No. 2,075,010B).
Accordingly, we have now made another approach to the synthesis of 3'-fluoro-3'-deoxykananycin A, and as a result of our researches we have now succeeded in synthetizing 3'-fluoro-3'-deoxykanamycin A first time by a synthetic process wherein 3-deoxy-3-fluoro-1,2:5,6-di-O-isopropylidene-.alpha.-D-glucofuranose, a known compound disclosed in the "Journal of Organic Chemistry" Vol. 43, No. 6, pages 1090-1092 (1978), is used as the starting compound and is subjected to a series of reaction steps as described hereinafter and illustrated with reference to Examples 1 to 3 given hereinafter. We have now further found that the 3'-fluoro-3'-deoxykanamycin A as synthetized by us is a new compound exhibiting antibacterial activities against gram-negative and gram-positive bacteria, including kanamycin-resistant bacterial strains.